Patients
67 patients with psoriasis who had no previous treatment for psoriasis (mean age: 43.33 ± 12.16 years) and 70 healthy subjects (mean age: 48.37 ± 14.99 years) were recruited from September 2015 to January 2018 in Tongde Hospital of Zhejiang Province. Patients with cardiovascular and cerebrovascular diseases, autoimmune diseases and other serious systemic diseases, pregnancy, lactation and so on were excluded. To evaluate disease type and severity, patients were all examined by dermatologist. Psoriasis Area Severity Index (PASI) scores were used. Individuals with PASI index ranging from 1 to 10 were considered as mild disease group, patients with PASI > 10 as moderate or severe group (12).
Informed consent was obtained from every patient with psoriasis and healthy individuals, and this study was approved by the Ethics Committee of Tongde Hospital of Zhejiang Province.
Cell culture
Human keratinocytes HaCaT cells were purchased from Cell Lines Service (Eppelheim, Germany). The cells were cultured in Dulbecco's modified Eagle's medium (DMEM; Invitrogen, Carlsbad, CA, USA) supplemented with 10% fetal bovine serum (FBS; Sigma-Aldrich, St Louis, MO, USA), and placed in a humidified atmosphere of 5% CO2 at 37 °C. TNF-alpha, IL-17A, IL-22, IL-1alpha, and Oncostatin-M (10 ng/mL, Prospec, East Brunswick, NJ) were included in the mixture of five proinflammatory cytokines (M5) (13). HaCaT cells were induced with M5, causing inflammation response and showing kinds of symptoms of psoriasis. The culture medium was changed every day. The cells were disaggregated and sub-cultured at a confluency of 70–90%.
Cell transfection
HaCaT cells were transfected with miR-106a-5p mimic, miR-106a-5p inhibitor and its negative control (miR-NC) using the Lipofectamine 2000 reagent (Invitrogen) in accordance with manufacturer protocols. The miR-106a-5p mimic, inhibitor and Negative Control were obtained from GenePharma (Shanghai, China). The qRT-PCR was performed for measuring the transfection efficiency. After 24 h transfection, HaCaT cells were treated with M5 (a cocktail of cytokines) for 24 h to induce psoriatic inflammation like condition.
Cell Culture
qRT-PCR assay
According to the manufacturer’s instructions, total RNA was isolated using TRIzol reagent (Invitrogen, USA). MiR-106a-5p was detected by reverse transcription of miRNA using a TaqMan MicroRNA Reverse Transcription Kit (Applied Biosystems, CA, USA), and measured by RT-PCR with the TaqMan MicroRNA Assay kit (Applied Biosystems, CA, USA) (14). U6 small nuclear RNA (U6 snRNA) was quantified as an endogenous reference. Experiments were performed in triplicate and run at least three times.
Enzyme-linked immunosorbent assay (ELISA)
Reference to the instructions of the manufacturer, the serum levels of IL-22, IL-17A, and TNF-alpha were detected by specific enzyme-linked immunosorbent (ELISA) kits (Beyotime Biotechnology, Shanghai, China). The absorbance was determined by enzyme labeling instrument (spectraMAX 340, Molecular Devices, Sunnyvale, CA, USA) at 450 nm.
Cell proliferation assay
The CCK-8 assay was performed to determine the effect of miR-106a-5p on the proliferation of HaCaT cells. Briefly, cells were seeded in 96-well plates at the density of 1 × 104 per well. After 24, 48 and 72 h, 20 µL of CCK-8 reagent were added into each well, and then incubated for 2 h at 37 °C. After all the treatment, the optical density values (OD) of each well was measured by a Microplate Reader (Bio-Rad, USA) at a wavelength of 450 nm, which could exhibit the proliferation capacity of the cells. The experiment was performed in triplicate.
Statistical analysis
The experimental data was expressed as mean ± standard deviation (SD). Statistical analysis of all data was used the SPSS 24.0 (SPSS Inc., Chicago, IL, USA) and GraphPad Prism 7.04 software (GraphPad, San Diego, CA, USA). The statistical differences between groups were compared by student’s t-test and one-way ANOVA analysis. Pearson’s correlation coefficient was applied for the correlation analysis. P < 0.05 was considered as a statistically significant criterion. Each experiment run at least three times.